All JS components subclassed from Ext.Component class should be registered in Ext's ComponentManager, like:

Ext.extend(org.ametys.widgets.RichTextWidget, org.ametys.form.TextAreaField, {});
[...]
Ext.ComponentMgr.registerType('rich-text', org.ametys.widgets.RichTextWidget);

This would allow tests such as component.isXType(type), which is recursive, i.e. richtext.isXType('textarea') returns true.